1. Field of the Invention
The present invention relates to a method of and an apparatus for continuously manufacturing molded slide fastener coupling elements of thermoplastic synthetic resin.
2. Prior Art
In a prior art shown in U.S. Pat. No. 4,406,849, issued on Sept. 27, 1983, a molded strip of coupling element blanks while still hot is folded by a single folder unit about its longitudinal axis into a U-shaped cross-section to provide semi-finished coupling heads, with legs on each side thereof. Then, the folded strip of blanks is shaped into a train of slide fastener coupling elements of a finalized shape and dimensions as it passes through a straight slot of a progressively constricted contour in a guide block while the legs are being concentrically heated. With such a single step of folding, the thermoplastic material of the strip of blanks is likely to be stretched unevenly which would result in a folded strip of blanks having an irregular shape and dimensions.